1. Field of the Invention
The present invention relates to a hand tool, and more particularly to a ratchet hand tool with an adjustable head that utilizes a sliding block to position and lock the adjustable head at a given angle.
2. Description of Related Art
Hand tools, especially for ratchet socket wrenches are extensively used to tighten or loosen fasteners. With reference to FIG. 11, a conventional ratchet socket wrench in accordance with prior art comprises a head (50), a handle (60), a pivot pin (512) and a head positioning device (66). The head (50) is adjustably mounted on the handle (60) with the head positioning device (66) and comprises a head body (51) and a socket ratchet drive (52). The head body (51) is pivotally mounted on the handle (60) with the pivot pin (512) and has multiple detents (511) formed and arranged about the pivot pin (512). The socket ratchet drive (52) is mounted in the head body (51). The handle (60) has a ball hole (61) and a blind hole (63). The ball hole (61) is longitudinally defined in the handle (60) and is aligned selectively with the detents (511). The blind hole (63) is defined transversely in the handle (60) and communicates with the ball hole (61).
The head positioning device (66) is movably mounted in the holes (61, 63) and comprises an engaging ball (62), a stepped rod (64) and an inner spring (65). The engaging ball (62) is mounted in the ball hole (61). The stepped rod (64) is slidably mounted in the blind hole (63) with the inner spring (65) and has an exterior surface and an annular groove (641) defined in the exterior surface. The exterior surface of the stepped rod (64) abuts the engaging ball (62) in the ball hole (61) to urge the engaging ball (62) into one of the detents (511).
The stepped rod (64) can be pushed inward the blind hole (63) to align the annular groove (641) with the engaging ball (62), which will simultaneously compress the inner spring (65). The engaging ball (62) will slip into the annular groove (641) and disengage from the detent (511) so that the head (50) can be adjusted to a given angle relative to the handle (60).
The compressed inner spring (65) pushes the stepped rod (64) outward so as to urge the engaging ball (62) into one of the detents (511) by the exterior surface of the stepped rod (64) when the stepped rod (64) is released. Therefore, the engaging ball (62) that engages one of the detents (511) will position and lock the head (50) at the given angle relative to the handle (60).
However, the conventional ratchet hand tools still have some shortcomings when manufacturing and using the hand tools.
First, the conventional hand tools are neither easy nor quick to fabricate and assemble, especially assembling the head positioning device (66). The handle (60) needs to have the positions of the holes (61, 63) precisely defined because if they are not manufacturing yields of the tools will be low and manufacturing costs will be excessive. In addition, assembling the engaging ball (62), the inner spring (65) and the stepped rod (64) is inconvenient and slow.
Second, the head positioning device (66) of the conventional hand tools uses simply the engaging ball (62) to engage one detent (511), whereby the engaging effect between the engaging ball (62) and the detent (511) is weak and unreliable.
Third, since it is difficult to adjust the head (50) using only a single hand, the conventional hand tools are inconvenient to use. A person must use both hands, i.e., one hand holds the handle (60) and the other hand pushes the stepped rod (64) inward the blind hole (63) to adjust the head (50) because the stepped rod (64) always needs to be pressed to allow the head (50) being adjustable. Thus, one-handed operations for adjusting the head (50) of the conventional tools are difficult.
To overcome the shortcomings, the present invention provides an improved ratchet hand tool having a sliding block to position and lock a head at a given angle relative to a handle of the ratchet hand tool to mitigate or obviate the aforementioned problems.